The micro-impulse generated by ablating an aluminum target in double-pulse laser bursts with different interpulse delays was investigated using a torsion pendulum.The plasma plume was simultaneously visualized using h...The micro-impulse generated by ablating an aluminum target in double-pulse laser bursts with different interpulse delays was investigated using a torsion pendulum.The plasma plume was simultaneously visualized using high-speed photography to analyze the coupling mechanism of the ablation impulse.The experiment was carried out using a pulsed laser with a pulse width of 8 ns and a wavelength of 1064 nm.The experimental results show that an impulse with an interpulse delay of 60 ns is roughly 60%higher than that with no delay between the two pulses,when the energy of both laser pulses is 50 m J.Therefore,double-pulse schemes could enhance the ablation impulse under certain conditions.This is because the ablation of the first laser pulse changes the optical properties of the aluminum target surface,increasing the absorptivity.However,the ablation impulse is reduced with a time delay of 20 ns when the energy of both laser pulses is100 mJ or 150 mJ.It can be concluded that the plasma produced by ablating the aluminum with the first pulse shields the second laser pulse.To summarize,the experimental results show that different delay times in a double-pulse scheme have a significant effect on the ablation impulse.The study provides a reference for the optimization of the parameters when laser ablation propulsion with a double-pulse scheme is applied in the fields of space debris removal,laser ablation thrusters,and so on.展开更多
Metal aluminum （A1） thin films are prepared by 2450 MHz electron cyclotron resonance plasma-assisted atomic layer deposition on glass and p-Si substrates using trimethylaluminum as the precursor and hydrogen as the ...Metal aluminum （A1） thin films are prepared by 2450 MHz electron cyclotron resonance plasma-assisted atomic layer deposition on glass and p-Si substrates using trimethylaluminum as the precursor and hydrogen as the reductive gas. We focus our attention on the plasma source for the thin-film preparation and annealing of the as-deposited films relative to the surface square resistivity. The square resistivity of as-deposited A1 films is greatly reduced after annealing and almost reaches the value of bulk metal. Through chemical and structural analysis, we conclude that the square resistivity is determined by neither the contaminant concentration nor the surface morphology, but by both the crystallinity and crystal size in this process.展开更多
Graphene-reinforced 7055 aluminum alloy composites with different contents of graphene were prepared by spark plasma sintering（SPS）. The structure and mechanical properties of the composites were investigated. Testi...Graphene-reinforced 7055 aluminum alloy composites with different contents of graphene were prepared by spark plasma sintering（SPS）. The structure and mechanical properties of the composites were investigated. Testing results show that the hardness, compressive strength, and yield strength of the composites are improved with the addition of 1wt% graphene. A clean, strong interface is formed between the metal matrix and graphene via metallurgical bonding on atomic scale. Harmful aluminum carbide（Al_4C_3） is not formed during SPS processing. Further addition of graphene（above 1wt%） results in the deterioration in mechanical properties of the composites. The agglomeration of graphene plates is exacerbated with increasing graphene content, which is the main reason for this deterioration.展开更多
aluminum alloy was implanted with nitrogen then titanium finally carbon by plasma-based ion implantatio to form a gradient layer. The structure and tribological properties of the layer were investigated. Its compositi...aluminum alloy was implanted with nitrogen then titanium finally carbon by plasma-based ion implantatio to form a gradient layer. The structure and tribological properties of the layer were investigated. Its composition profiles and chemical states were analyzed with X-ray photoelectron spectroscopy(XPS). The surface carbon layer was analyzed by Raman spectrum. The appearances were observed by atomic force microscope (AFM). The surface hardness was measured with the mechanical property microprobe. The dry wear tests against GCr15 steel ball at various sliding loads were performed with a ball-on-disk wear tester in ambient environment. The results show that the thickness of the modified layer is 1 200 nm, the carbon layer is a smooth and compact diamond-like carbon(DLC) films, and the carbon-titanium interface is broadened due to carbon ions implantation, resulting in a good composition and structure transition between DLC films and titanium layer. Surface hardness is improved markedly, with a slow and uniform change. Tribological properties are improved greatly although they reduce with the increase of sliding loads because the modified layer becomes thin rapidly.展开更多
Plasma electrolytic oxidation(PEO) coatings were fabricated on 6063 aluminum alloy in a cheap and convenient electrolyte. The effect of different current densities, i e, 5, 10, 15, and 20 A/dm2on the microstructure an...Plasma electrolytic oxidation(PEO) coatings were fabricated on 6063 aluminum alloy in a cheap and convenient electrolyte. The effect of different current densities, i e, 5, 10, 15, and 20 A/dm2on the microstructure and corrosion behavior of coatings was comprehensively studied by scanning electron microscopy(SEM), stereoscopic microscopy, potentiodynamic polarization and electrochemical impedance spectroscopy(EIS), respectively. It is found that the pore density decreases and the pore size increases with increasing current density. The XRD results show that the coatings are only composed of α-Al2O3and γ-Al2O3. Potentiodynamic polarization test proves that the coating formed under 10 A/dm2possesses the best anticorrosion property. The long time EIS test shows that the coating under 10 A/dm2is able to protect the aluminum alloy substrate after long time of immersion in 0.59 M NaCl solution, which confirms the salt solution immersion test results in 2 M NaCl solution.展开更多
This paper presents the results of aluminum surface treatment by diffuse coplanar surface barrier discharge. The goals are to study the effectiveness of the plasma treatment and the dependence of its efficiency on ope...This paper presents the results of aluminum surface treatment by diffuse coplanar surface barrier discharge. The goals are to study the effectiveness of the plasma treatment and the dependence of its efficiency on operation parameters, such as sample-to-electrode distance, treatment time or gas atmosphere. Three types of aluminum materials （bricks, sheets and thin films） were tested to ensure the reliability of the treatment. The changes in the surface properties were characterized by the surface free energy, atomic force microscopy, attenuated total reflectance Fourier transform infrared spectroscopy （ATR FTIR） and X-ray photoelectron spec- troscopy （XPS）. The influence of aging effect on the treatment was also measured and discussed.展开更多
Plasma-MIG {metal inert gas arc welding） hybrid welding of aluminum alloy with 6 mm thickness using ER5356 welding wire was carried out. The microstructures and mechanical properties of the welded joint were inve...Plasma-MIG {metal inert gas arc welding） hybrid welding of aluminum alloy with 6 mm thickness using ER5356 welding wire was carried out. The microstructures and mechanical properties of the welded joint were investigated by optical microscopy, X-ray diffraction （XRD） , energy dispersive spectroscopy （EDS） , tensile test, hardness test and scanning electron microscope （ SEM） were used to judge the type of tensile fracture. The results showed that the tensile strength of welded joint was 142 MPa which was 53. 6% o f the strength o f the base metal. The welding seam zone was characterized by dendritic structure. In the fusion zone, the columnar grains existed at one side of the welding seam. The fibrous organization was found in the base metal, and also in the heat affected zone （HAZ） where the recrystallization occurred. The HAZ was the weakest position of the welded joint due to the coarsening of Mg2Si phase. The type of tensile fracture was ductile fracture.展开更多
A double invert variable polarity plasma arc （VPPA） power source based on 16-bit MCU applied for aluminum alloys was developed. Mechanics, electrical and the produced heat mechanism of VPPAW arc were tested and anal...A double invert variable polarity plasma arc （VPPA） power source based on 16-bit MCU applied for aluminum alloys was developed. Mechanics, electrical and the produced heat mechanism of VPPAW arc were tested and analyzed. Results indicate that during the VPPA welding procedure of aluminum alloy, the arc of electrode negative （EN） has more effect on force, whereas the arc of electrode positive （ EP ） has more effect on heat. It should be noted that keeping the balance of the force and heat is the critical element of VPPAW. This power source had been successfully used to weld aluminum alloy with a 15 mm thickness in vertical welding. The conclusions are applicable to the variable polarity plasma arc welding technique used in the aerospace industry.展开更多
Reliable surface treatment has been explored to improve the strength and wear resistance of aluminum alloy parts in automotives. Long duration time as well as long pre-sputtering time are required for plasma nitriding...Reliable surface treatment has been explored to improve the strength and wear resistance of aluminum alloy parts in automotives. Long duration time as well as long pre-sputtering time are required for plasma nitriding of aluminum or its alloys only with the thickness of a few micrometers. New plasma inner nitriding is proposed to realize the fast-rate nitriding of aluminum alloys. Al-6Cu alloy is employed as a targeting material in order to demonstrate the effectiveness of this plasma nitriding. Mechanism of fast-rate nitriding process is discussed with consideration of the role of Al2Cu precipitates.展开更多
High-temperature ignition is essential for the ignition and combustion of energetic metal fuels, including aluminum and magnesium particles which are protected by their high- melting-temperature oxides. A plasma torch...High-temperature ignition is essential for the ignition and combustion of energetic metal fuels, including aluminum and magnesium particles which are protected by their high- melting-temperature oxides. A plasma torch characterized by an ultrahigh-temperature plasma plume fulfills such high-temperature ignition conditions. A new steam plasma igniter is designed and successfully validated by aluminum power ignition and combustion tests. The steam plasma rapidly stabilizes in both plasma and steam jet modes. Parametric investigation of the steam plasma jet is conducted in terms of arc strength. A high-speed camera and an oscilloscope method visualize the discharge characteristics, and optical emission spectroscopy measures the thermochemical properties of the plasma jet. The diatomic molecule OH fitting method, the Boltzmann plot method, and short exposure capturing with an intensified charge coupled device record the axial distributions of the rotational gas temperature, excitation temperature, and OH radical distribution, respectively. The excitation temperature at the nozzle tip is near 5500 K, and the gas temperature is 5400 K.展开更多
Thick and hard ceramic coatings were fabricated on A356 aluminum alloy by using plasma electrolytic oxidation(PEO) technique. The microstructure and phase composition of the PEO coatings were examined by using SEM and...Thick and hard ceramic coatings were fabricated on A356 aluminum alloy by using plasma electrolytic oxidation(PEO) technique. The microstructure and phase composition of the PEO coatings were examined by using SEM and XRD method. It is found that the PEO coatings are mainly composed of crystalline α-Al2O3 and mullite. The dry sliding wear test of PEO coatings were carried out on a ring-on-ring wear machine. Results shows that there is hardly no wear loss of polished PEO coatings while the wear rate of uncoated aluminum alloy is 4.3×10-5 mm3·(N·m)-1 at a speed of 0.52 m·s-1 and a load of 40 N.展开更多
Amorphous [Al-Si-O] coatings were deposited on aluminum alloy by plasma electrolytic oxidation (PEO). The process parameters, composition, micrograph, and mechanical property of PEO amorphous coatings were investigate...Amorphous [Al-Si-O] coatings were deposited on aluminum alloy by plasma electrolytic oxidation (PEO). The process parameters, composition, micrograph, and mechanical property of PEO amorphous coatings were investigated. It is found that the growth rate of PEO coatings reaches 4.44 μm/min if the current density is 0.9 mA/mm2. XRD results show that the PEO coatings are amorphous in the current density range of 0.3 - 0.9mA/mm2. EDS results show that the coatings are composed of O, Si and Al elements. SEM results show that the coatings are porous. Nano indentation results show that the hardness of the coatings is about 3 - 4 times of that of the substrate, while the elastic modulus is about the same with the substrate. Furthermore, a formation mechanism of amorphous PEO coatings was proposed.展开更多
aluminum alloy was implanted with nitrogen then titanium at different titanium target sputtering currents by plasma-based ion implantation(PBII). The appearances were observed by atomic force microscope, and the surfa...aluminum alloy was implanted with nitrogen then titanium at different titanium target sputtering currents by plasma-based ion implantation(PBII). The appearances were observed by atomic force microscope, and the surface hardness was measured with Knoop hardness tester and the mechanical property microprobe. Ball-on-disc dry wear experiments were performed under ambient air conditions, to study the tribological properties of the modified layers against GCr15 steel ball, employing various loads and a constant sliding speed. After dual modifications, surface hardness at 100 nm depth could reach to 9 GPa, increasing by about 5 times; tribological properties at lower load(e.g. 1 N) were obviously improved, with the friction coefficient(below 0.2) decreasing by over 60%, and the wear life(800 times) increasing by about 5 times. Meanwhile, with the increase of the sputtering current, the appearance is smooth, the surface hardness tends to a slow and even variation, the wear life presents a parabola-like change, and the friction coefficient and the adhesive wear degree decrease. However, tribological properties are reduced with the increase of the load due to the modified layer rapidly getting thin.展开更多
As the important evaluation parameters concerning the spray qualities, the porosity and surface roughness of the coatings obtained by thermal spray forming have great influence on their forming accuracy, mechanical pr...As the important evaluation parameters concerning the spray qualities, the porosity and surface roughness of the coatings obtained by thermal spray forming have great influence on their forming accuracy, mechanical properties and service lifetime. But it is difficult to predict or control the two parameters for such a highly nonlinear process. A two-dimensional simulation of coating porosity and surface roughness of nickel-aluminum alloy (Ni-5%Al) in plasma spray forming was presented, which was based on the multi-dimensional statistical behaviors of the droplets as well as the simplification and digitization of the typical splat cross sections. Further analysis involving the influence of the droplet diameters and the scanning velocities of the spray gun on the two parameters was conducted. The simulation and analysis results indicate that the porosity and surface roughness are more influenced by the droplet diameters, but less influenced by the spray gun velocities. The results will provide basis for the prediction or control of coating mechanical properties by depositing parameters.展开更多
An inductively coupled plasma (ICP) discharge and its etching behaviors for aluminum alloys were investigated in this report. A radio frequency power supply was used for plasma generation. The unique hardware configur...An inductively coupled plasma (ICP) discharge and its etching behaviors for aluminum alloys were investigated in this report. A radio frequency power supply was used for plasma generation. The unique hardware configuration enabled one to control ion energy separately from plasma density. Plasma properties were measured with a Langmuir probe. Electron temperature, plasma potential and plasma density were found to be comparable with those reported from Electron Cyclotron Resonance (ECR) and other types of reactors[1].A mixture of HBr and chlorine gases were used for this aluminum etch study. Experimental matrices were designed with Response Surface Methodology (RSM) to analyze the process trends versus etch parameters, such as source power, bias power and gas composition. An etch rate of 8500A to 9000A per minute was obtained at 5 to 15 mTorr pressure ranges. Anisotropic profiles with high photoresist selectivity (5 to 1) and silicon dioxide selectivity greater than 10 were achieved with HBr addition into chlorine plasma.Bromine-containing chemistry for an aluminum etch in a low pressure ICP discharge showed great potential for use in ULSI fabrication. In addition, the hardware used was very simple and the chamber size was much smaller than other high density plasma sources.展开更多
This paper is aimed to show the influence of initial chemical pretreatment prior to subsequent plasma activation of aluminum surfaces.The results of our study showed that the state of the topmost surface layer（i.e.th...This paper is aimed to show the influence of initial chemical pretreatment prior to subsequent plasma activation of aluminum surfaces.The results of our study showed that the state of the topmost surface layer（i.e.the surface morphology and chemical groups）of plasma modified aluminum significantly depends on the chemical precleaning.Commonly used chemicals（isopropanol,trichlorethane,solution of Na OH in deionized water）were used as precleaning agents.The plasma treatments were done using a radio frequency driven atmospheric pressure plasma pencil developed at Masaryk University,which operates in Ar,Ar/O_2 gas mixtures.The effectiveness of the plasma treatment was estimated by the wettability measurements,showing high wettability improvement already after 0.3 s treatment.The effects of surface cleaning（hydrocarbon removal）,surface oxidation and activation（generation of OH groups）were estimated using infrared spectroscopy.The changes in the surface morphology were measured using scanning electron microscopy.Optical emission spectroscopy measurements in the near-to-surface region with temperature calculations showed that plasma itself depends on the sample precleaning procedure.展开更多
Nitriding of surface of aluminum alloys was carried out with using an electron-beam-excited-plasma (EBEP) technique. The EBEP is sustained by electron impact ionization with energetic electron beam. Two kinds of subst...Nitriding of surface of aluminum alloys was carried out with using an electron-beam-excited-plasma (EBEP) technique. The EBEP is sustained by electron impact ionization with energetic electron beam. Two kinds of substrates, aluminum alloys AA5052 and AA5083, were exposed to the down flow of EBEP source at 843 K for 45min. The specimens were characterized with respect to following properties: crystallographic structure (XRD), morphology (SEM) and the cross sectional microstructures of the nitrided layer was observed using a scanning electron microscopy (SEM). There are some A12O3 particles on the surface of the nitrided AA5052 and AA5083. The A1N layers were formed on the substrates with the thickness of 4.5 fi m for AA5052 and 0.5 /z m for AA5083 . A relatively uniform nitrided surface layer composed of A1N can be observed on the AA5052 substrate. The grains size near the interfaces between the substrate and A1N layer were smaller than that near the surface. On the surface of A1N layer, the concentration of nitrogen was high and in the middle of A1N layer it had a constant concentration like the aluminum and the concentration was decreased with approaching to the interface. On the surface of nitrided AA5083, a uniform A1N layer was not formed as the reason for the high nitriding temperature.展开更多
The corrosion-protective performance of plasma-polymerized (PP) coatings on pretreated aluminum substrates has been investigated by cathodic polarization curve measurement. The surface composition and electronic prope...The corrosion-protective performance of plasma-polymerized (PP) coatings on pretreated aluminum substrates has been investigated by cathodic polarization curve measurement. The surface composition and electronic properties of the pretreated and PP film coated metal surfaces were also characterized by XPS and the temperature-programmed photoelectron emission (TPPE). A PP coating was prepared on the pretreated surfaces by plasma polymerization of a mixture of tetraethoxysilane (TEOS) monomer vapor and oxygen using a 13.56MHz radiofrequency generator. The polarization curve of PP film coated samples was measured in NaCl aqueous solution. The weight loss rate calculated from the value of the corrosion current of the curve was used to estimate the protective performance of the PP film coated samples. Argon plasma treatment of the metal surface gave much better corrosion-protective performance than pretreatments such as oxidation by heating in air and diamond scratching. The XPS analysis indicated that the silicon oxide assigned to SiO2 was formed on the PP film coated surface. The TPPE analysis revealed that the electron emission characteristics for the metal surfaces pretreated only were strongly influenced by the pretreatments, while all the PP film coated samples exhibited nearly the same electron emission trend with a much decreased intensity.展开更多
Effects of calcium on ATPase activities, lipid contents, and fatty acid compositions of plasma membrane from wheat roots were assayed under aluminum stress. The results showed that the increase of calcium concentr...Effects of calcium on ATPase activities, lipid contents, and fatty acid compositions of plasma membrane from wheat roots were assayed under aluminum stress. The results showed that the increase of calcium concentration in the nutrient solution increased the activity of H + ATPase and the phospholipid content, decreased the activity of Ca 2+ ATPase and the galactolipid of plasma membrane. Owing to the decrease of linolenic acid content, the index of unsaturated fatty acid (IUFA) and index of double bond (DBI) decreased in Altas66. The IUFA and DBI of plasma membrane from Scout66 roots increased because its linolenic acid content increased obviously and its palmitic acid content decreased apparently.展开更多
Ultra-fine aluminum nitride has been synthesized by the evaporation of aluminum powder at atmospheric-pressure nitrogen plasma in a hot-wall reactor. The average size of aluminum nitride particle is 0.11 μm measured ...Ultra-fine aluminum nitride has been synthesized by the evaporation of aluminum powder at atmospheric-pressure nitrogen plasma in a hot-wall reactor. The average size of aluminum nitride particle is 0.11 μm measured by scanning electric mirror (SEM), and the purity is at least over 90% evaluated by X-Ray diffraction (XRD). The conversion of Al powder to aluminum nitride is strongly depended on the injection of NH3. Typical experimental parameters such as the feed rate of raw material, the flow rate of ammonia and the position of injecting aluminum powder into the reactor are given.展开更多
基金supported by National Natural Science Foundation of China(Nos.11502301 and 11602304)。
文摘The micro-impulse generated by ablating an aluminum target in double-pulse laser bursts with different interpulse delays was investigated using a torsion pendulum.The plasma plume was simultaneously visualized using high-speed photography to analyze the coupling mechanism of the ablation impulse.The experiment was carried out using a pulsed laser with a pulse width of 8 ns and a wavelength of 1064 nm.The experimental results show that an impulse with an interpulse delay of 60 ns is roughly 60%higher than that with no delay between the two pulses,when the energy of both laser pulses is 50 m J.Therefore,double-pulse schemes could enhance the ablation impulse under certain conditions.This is because the ablation of the first laser pulse changes the optical properties of the aluminum target surface,increasing the absorptivity.However,the ablation impulse is reduced with a time delay of 20 ns when the energy of both laser pulses is100 mJ or 150 mJ.It can be concluded that the plasma produced by ablating the aluminum with the first pulse shields the second laser pulse.To summarize,the experimental results show that different delay times in a double-pulse scheme have a significant effect on the ablation impulse.The study provides a reference for the optimization of the parameters when laser ablation propulsion with a double-pulse scheme is applied in the fields of space debris removal,laser ablation thrusters,and so on.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11175024)the Beijing Natural Science Foundation, China (Grant No. 1112012)+1 种基金the Science and Technology on Surface Engineering Laboratorythe Beijing Education Committee, China (Grant Nos. BM201002, 2011BAD24B01, KM201110015008, KM201010015005, and PHR20110516)
文摘Metal aluminum （A1） thin films are prepared by 2450 MHz electron cyclotron resonance plasma-assisted atomic layer deposition on glass and p-Si substrates using trimethylaluminum as the precursor and hydrogen as the reductive gas. We focus our attention on the plasma source for the thin-film preparation and annealing of the as-deposited films relative to the surface square resistivity. The square resistivity of as-deposited A1 films is greatly reduced after annealing and almost reaches the value of bulk metal. Through chemical and structural analysis, we conclude that the square resistivity is determined by neither the contaminant concentration nor the surface morphology, but by both the crystallinity and crystal size in this process.
基金financially supported by the National Natural Science Foundation of China (No. 51271012)
文摘Graphene-reinforced 7055 aluminum alloy composites with different contents of graphene were prepared by spark plasma sintering（SPS）. The structure and mechanical properties of the composites were investigated. Testing results show that the hardness, compressive strength, and yield strength of the composites are improved with the addition of 1wt% graphene. A clean, strong interface is formed between the metal matrix and graphene via metallurgical bonding on atomic scale. Harmful aluminum carbide（Al_4C_3） is not formed during SPS processing. Further addition of graphene（above 1wt%） results in the deterioration in mechanical properties of the composites. The agglomeration of graphene plates is exacerbated with increasing graphene content, which is the main reason for this deterioration.
文摘aluminum alloy was implanted with nitrogen then titanium finally carbon by plasma-based ion implantatio to form a gradient layer. The structure and tribological properties of the layer were investigated. Its composition profiles and chemical states were analyzed with X-ray photoelectron spectroscopy(XPS). The surface carbon layer was analyzed by Raman spectrum. The appearances were observed by atomic force microscope (AFM). The surface hardness was measured with the mechanical property microprobe. The dry wear tests against GCr15 steel ball at various sliding loads were performed with a ball-on-disk wear tester in ambient environment. The results show that the thickness of the modified layer is 1 200 nm, the carbon layer is a smooth and compact diamond-like carbon(DLC) films, and the carbon-titanium interface is broadened due to carbon ions implantation, resulting in a good composition and structure transition between DLC films and titanium layer. Surface hardness is improved markedly, with a slow and uniform change. Tribological properties are improved greatly although they reduce with the increase of sliding loads because the modified layer becomes thin rapidly.
基金Funded by the National Natural Science Foundation of China(Nos.51371039 and 51871031)
文摘Plasma electrolytic oxidation(PEO) coatings were fabricated on 6063 aluminum alloy in a cheap and convenient electrolyte. The effect of different current densities, i e, 5, 10, 15, and 20 A/dm2on the microstructure and corrosion behavior of coatings was comprehensively studied by scanning electron microscopy(SEM), stereoscopic microscopy, potentiodynamic polarization and electrochemical impedance spectroscopy(EIS), respectively. It is found that the pore density decreases and the pore size increases with increasing current density. The XRD results show that the coatings are only composed of α-Al2O3and γ-Al2O3. Potentiodynamic polarization test proves that the coating formed under 10 A/dm2possesses the best anticorrosion property. The long time EIS test shows that the coating under 10 A/dm2is able to protect the aluminum alloy substrate after long time of immersion in 0.59 M NaCl solution, which confirms the salt solution immersion test results in 2 M NaCl solution.
基金supported by the Czech Science Foundation(Project No.104/08/02290)
文摘This paper presents the results of aluminum surface treatment by diffuse coplanar surface barrier discharge. The goals are to study the effectiveness of the plasma treatment and the dependence of its efficiency on operation parameters, such as sample-to-electrode distance, treatment time or gas atmosphere. Three types of aluminum materials （bricks, sheets and thin films） were tested to ensure the reliability of the treatment. The changes in the surface properties were characterized by the surface free energy, atomic force microscopy, attenuated total reflectance Fourier transform infrared spectroscopy （ATR FTIR） and X-ray photoelectron spec- troscopy （XPS）. The influence of aging effect on the treatment was also measured and discussed.
基金Key Laboratory of Advanced Welding Technology of Jiangsu University of Science and Technology (Grant NO. JSAWT-11-02) for its financial support
文摘Plasma-MIG {metal inert gas arc welding） hybrid welding of aluminum alloy with 6 mm thickness using ER5356 welding wire was carried out. The microstructures and mechanical properties of the welded joint were investigated by optical microscopy, X-ray diffraction （XRD） , energy dispersive spectroscopy （EDS） , tensile test, hardness test and scanning electron microscope （ SEM） were used to judge the type of tensile fracture. The results showed that the tensile strength of welded joint was 142 MPa which was 53. 6% o f the strength o f the base metal. The welding seam zone was characterized by dendritic structure. In the fusion zone, the columnar grains existed at one side of the welding seam. The fibrous organization was found in the base metal, and also in the heat affected zone （HAZ） where the recrystallization occurred. The HAZ was the weakest position of the welded joint due to the coarsening of Mg2Si phase. The type of tensile fracture was ductile fracture.
基金This work was supported by the National Nature Science Foundation of China （ Grant No. 50764007）.
文摘A double invert variable polarity plasma arc （VPPA） power source based on 16-bit MCU applied for aluminum alloys was developed. Mechanics, electrical and the produced heat mechanism of VPPAW arc were tested and analyzed. Results indicate that during the VPPA welding procedure of aluminum alloy, the arc of electrode negative （EN） has more effect on force, whereas the arc of electrode positive （ EP ） has more effect on heat. It should be noted that keeping the balance of the force and heat is the critical element of VPPAW. This power source had been successfully used to weld aluminum alloy with a 15 mm thickness in vertical welding. The conclusions are applicable to the variable polarity plasma arc welding technique used in the aerospace industry.
基金supported in part by the Grand-in-Aid from MEXT with the contract number of#12305047the national project on the environmentally benign manufacturing from MEXT.
文摘Reliable surface treatment has been explored to improve the strength and wear resistance of aluminum alloy parts in automotives. Long duration time as well as long pre-sputtering time are required for plasma nitriding of aluminum or its alloys only with the thickness of a few micrometers. New plasma inner nitriding is proposed to realize the fast-rate nitriding of aluminum alloys. Al-6Cu alloy is employed as a targeting material in order to demonstrate the effectiveness of this plasma nitriding. Mechanism of fast-rate nitriding process is discussed with consideration of the role of Al2Cu precipitates.
基金supported by the Defense Acquisition Program Administration and Agency for Defense Development under the contract UD110095CDsupported by the Advanced Research Center Program(NRF-2013R1A5A1073861) through the National Research Foundation of Korea(NRF) grant funded by the Korean government(MSIP) contracted through the Advanced Space Propulsion Research Center at Seoul National University
文摘High-temperature ignition is essential for the ignition and combustion of energetic metal fuels, including aluminum and magnesium particles which are protected by their high- melting-temperature oxides. A plasma torch characterized by an ultrahigh-temperature plasma plume fulfills such high-temperature ignition conditions. A new steam plasma igniter is designed and successfully validated by aluminum power ignition and combustion tests. The steam plasma rapidly stabilizes in both plasma and steam jet modes. Parametric investigation of the steam plasma jet is conducted in terms of arc strength. A high-speed camera and an oscilloscope method visualize the discharge characteristics, and optical emission spectroscopy measures the thermochemical properties of the plasma jet. The diatomic molecule OH fitting method, the Boltzmann plot method, and short exposure capturing with an intensified charge coupled device record the axial distributions of the rotational gas temperature, excitation temperature, and OH radical distribution, respectively. The excitation temperature at the nozzle tip is near 5500 K, and the gas temperature is 5400 K.
基金This work was financially supported by the Fund of Beijing Jiaotong University,and by the OpenFund of State Key Laboratory of Tribology of China(No.SKLT02-4).
文摘Thick and hard ceramic coatings were fabricated on A356 aluminum alloy by using plasma electrolytic oxidation(PEO) technique. The microstructure and phase composition of the PEO coatings were examined by using SEM and XRD method. It is found that the PEO coatings are mainly composed of crystalline α-Al2O3 and mullite. The dry sliding wear test of PEO coatings were carried out on a ring-on-ring wear machine. Results shows that there is hardly no wear loss of polished PEO coatings while the wear rate of uncoated aluminum alloy is 4.3×10-5 mm3·(N·m)-1 at a speed of 0.52 m·s-1 and a load of 40 N.
文摘Amorphous [Al-Si-O] coatings were deposited on aluminum alloy by plasma electrolytic oxidation (PEO). The process parameters, composition, micrograph, and mechanical property of PEO amorphous coatings were investigated. It is found that the growth rate of PEO coatings reaches 4.44 μm/min if the current density is 0.9 mA/mm2. XRD results show that the PEO coatings are amorphous in the current density range of 0.3 - 0.9mA/mm2. EDS results show that the coatings are composed of O, Si and Al elements. SEM results show that the coatings are porous. Nano indentation results show that the hardness of the coatings is about 3 - 4 times of that of the substrate, while the elastic modulus is about the same with the substrate. Furthermore, a formation mechanism of amorphous PEO coatings was proposed.
文摘aluminum alloy was implanted with nitrogen then titanium at different titanium target sputtering currents by plasma-based ion implantation(PBII). The appearances were observed by atomic force microscope, and the surface hardness was measured with Knoop hardness tester and the mechanical property microprobe. Ball-on-disc dry wear experiments were performed under ambient air conditions, to study the tribological properties of the modified layers against GCr15 steel ball, employing various loads and a constant sliding speed. After dual modifications, surface hardness at 100 nm depth could reach to 9 GPa, increasing by about 5 times; tribological properties at lower load(e.g. 1 N) were obviously improved, with the friction coefficient(below 0.2) decreasing by over 60%, and the wear life(800 times) increasing by about 5 times. Meanwhile, with the increase of the sputtering current, the appearance is smooth, the surface hardness tends to a slow and even variation, the wear life presents a parabola-like change, and the friction coefficient and the adhesive wear degree decrease. However, tribological properties are reduced with the increase of the load due to the modified layer rapidly getting thin.
基金Project(50675072) supported by the National Natural Science Foundation of ChinaProject(2006J0165) supported by the Natural Science Foundation of Fujian Province of ChinaProject(20062178) supported by the Natural Science Foundation of Liaoning Province of China
文摘As the important evaluation parameters concerning the spray qualities, the porosity and surface roughness of the coatings obtained by thermal spray forming have great influence on their forming accuracy, mechanical properties and service lifetime. But it is difficult to predict or control the two parameters for such a highly nonlinear process. A two-dimensional simulation of coating porosity and surface roughness of nickel-aluminum alloy (Ni-5%Al) in plasma spray forming was presented, which was based on the multi-dimensional statistical behaviors of the droplets as well as the simplification and digitization of the typical splat cross sections. Further analysis involving the influence of the droplet diameters and the scanning velocities of the spray gun on the two parameters was conducted. The simulation and analysis results indicate that the porosity and surface roughness are more influenced by the droplet diameters, but less influenced by the spray gun velocities. The results will provide basis for the prediction or control of coating mechanical properties by depositing parameters.
文摘An inductively coupled plasma (ICP) discharge and its etching behaviors for aluminum alloys were investigated in this report. A radio frequency power supply was used for plasma generation. The unique hardware configuration enabled one to control ion energy separately from plasma density. Plasma properties were measured with a Langmuir probe. Electron temperature, plasma potential and plasma density were found to be comparable with those reported from Electron Cyclotron Resonance (ECR) and other types of reactors[1].A mixture of HBr and chlorine gases were used for this aluminum etch study. Experimental matrices were designed with Response Surface Methodology (RSM) to analyze the process trends versus etch parameters, such as source power, bias power and gas composition. An etch rate of 8500A to 9000A per minute was obtained at 5 to 15 mTorr pressure ranges. Anisotropic profiles with high photoresist selectivity (5 to 1) and silicon dioxide selectivity greater than 10 were achieved with HBr addition into chlorine plasma.Bromine-containing chemistry for an aluminum etch in a low pressure ICP discharge showed great potential for use in ULSI fabrication. In addition, the hardware used was very simple and the chamber size was much smaller than other high density plasma sources.
基金the Czech Science Foundation(Project No.104/08/02290)the Czech Ministry of Industry and Trade(Project CZ.1.03/5.1.00/12.00010)the Czech Ministry of Education(Project MSM0021622411)
文摘This paper is aimed to show the influence of initial chemical pretreatment prior to subsequent plasma activation of aluminum surfaces.The results of our study showed that the state of the topmost surface layer（i.e.the surface morphology and chemical groups）of plasma modified aluminum significantly depends on the chemical precleaning.Commonly used chemicals（isopropanol,trichlorethane,solution of Na OH in deionized water）were used as precleaning agents.The plasma treatments were done using a radio frequency driven atmospheric pressure plasma pencil developed at Masaryk University,which operates in Ar,Ar/O_2 gas mixtures.The effectiveness of the plasma treatment was estimated by the wettability measurements,showing high wettability improvement already after 0.3 s treatment.The effects of surface cleaning（hydrocarbon removal）,surface oxidation and activation（generation of OH groups）were estimated using infrared spectroscopy.The changes in the surface morphology were measured using scanning electron microscopy.Optical emission spectroscopy measurements in the near-to-surface region with temperature calculations showed that plasma itself depends on the sample precleaning procedure.
文摘Nitriding of surface of aluminum alloys was carried out with using an electron-beam-excited-plasma (EBEP) technique. The EBEP is sustained by electron impact ionization with energetic electron beam. Two kinds of substrates, aluminum alloys AA5052 and AA5083, were exposed to the down flow of EBEP source at 843 K for 45min. The specimens were characterized with respect to following properties: crystallographic structure (XRD), morphology (SEM) and the cross sectional microstructures of the nitrided layer was observed using a scanning electron microscopy (SEM). There are some A12O3 particles on the surface of the nitrided AA5052 and AA5083. The A1N layers were formed on the substrates with the thickness of 4.5 fi m for AA5052 and 0.5 /z m for AA5083 . A relatively uniform nitrided surface layer composed of A1N can be observed on the AA5052 substrate. The grains size near the interfaces between the substrate and A1N layer were smaller than that near the surface. On the surface of A1N layer, the concentration of nitrogen was high and in the middle of A1N layer it had a constant concentration like the aluminum and the concentration was decreased with approaching to the interface. On the surface of nitrided AA5083, a uniform A1N layer was not formed as the reason for the high nitriding temperature.
文摘The corrosion-protective performance of plasma-polymerized (PP) coatings on pretreated aluminum substrates has been investigated by cathodic polarization curve measurement. The surface composition and electronic properties of the pretreated and PP film coated metal surfaces were also characterized by XPS and the temperature-programmed photoelectron emission (TPPE). A PP coating was prepared on the pretreated surfaces by plasma polymerization of a mixture of tetraethoxysilane (TEOS) monomer vapor and oxygen using a 13.56MHz radiofrequency generator. The polarization curve of PP film coated samples was measured in NaCl aqueous solution. The weight loss rate calculated from the value of the corrosion current of the curve was used to estimate the protective performance of the PP film coated samples. Argon plasma treatment of the metal surface gave much better corrosion-protective performance than pretreatments such as oxidation by heating in air and diamond scratching. The XPS analysis indicated that the silicon oxide assigned to SiO2 was formed on the PP film coated surface. The TPPE analysis revealed that the electron emission characteristics for the metal surfaces pretreated only were strongly influenced by the pretreatments, while all the PP film coated samples exhibited nearly the same electron emission trend with a much decreased intensity.
文摘Effects of calcium on ATPase activities, lipid contents, and fatty acid compositions of plasma membrane from wheat roots were assayed under aluminum stress. The results showed that the increase of calcium concentration in the nutrient solution increased the activity of H + ATPase and the phospholipid content, decreased the activity of Ca 2+ ATPase and the galactolipid of plasma membrane. Owing to the decrease of linolenic acid content, the index of unsaturated fatty acid (IUFA) and index of double bond (DBI) decreased in Altas66. The IUFA and DBI of plasma membrane from Scout66 roots increased because its linolenic acid content increased obviously and its palmitic acid content decreased apparently.
基金This work was supported by Science and Technology Innovation Fund of Middle-Minor Enterprises from Ministy of Science and Technology.
文摘Ultra-fine aluminum nitride has been synthesized by the evaporation of aluminum powder at atmospheric-pressure nitrogen plasma in a hot-wall reactor. The average size of aluminum nitride particle is 0.11 μm measured by scanning electric mirror (SEM), and the purity is at least over 90% evaluated by X-Ray diffraction (XRD). The conversion of Al powder to aluminum nitride is strongly depended on the injection of NH3. Typical experimental parameters such as the feed rate of raw material, the flow rate of ammonia and the position of injecting aluminum powder into the reactor are given.
